Method of epidural surgery

ABSTRACT

A method of epidural surgery is provided that improves visibility in the epidural space of a patient for more effectively conducting therapeutic surgery therein. The method includes the steps of distending a portion of the epidural space of a patient by filling the portion of the epidural space with a fluid supplied from a catheter and positioning a portion of an optical scope in the distended portion of the epidural space by inserting the optical scope through the same catheter that supplies the distending fluid to thereby provide a visual image of the epidural space.

RELATED APPLICATIONS

This application is a continuation of Ser. No. 09/066,884 filed on Apr. 27, 1998 now U.S. Pat. No. 6,010,493, which is a continuation of U.S. Ser. No. 08/957,998, filed Oct. 22, 1997, now U.S. Pat. No. 5,857,996, which is a continuation of U.S. Ser. No. 08/606,084 filed Feb. 23, 1996, now ABN, which is a continuation of U.S. Ser. No. 08/321,174 filed Oct. 11, 1994, now U.S. Pat. No. 5,496,269, which is a continuation of U.S. Ser. No. 08/129,331, filed Sep. 30, 1993, now U.S. Pat. No. 5,354,266 which is a continuation-in-part of U.S. Ser. No. 07/908,403, filed Jul. 6, 1992, now U.S. Pat. No. 5,342,299, which is a continuation-in-part of U.S. Ser. No. 07/963,431 filed Oct. 19, 1992, now U.S. Pat. No. 5,423,311, which is a continuation-in-part of U.S. Ser. No. 07/970,490 filed Nov. 2, 1992 now U.S. Pat. No. 5,399,164.

FIELD OF THE INVENTION

This invention relates to surgical methods, and more particularly to methods of epidural surgery in and around the epidural space.

BACKGROUND OF THE INVENTION

Back pain, and particularly lower back pain, is a major expense to society and is one of the most common disabling problems of those of working age. Injuries to the back vary from herniated disks of the spine to muscle strains and nerve damage. In the back or posterior end of the human body, the epidural space is potential space located in and extending the length of the spine. The epidural space is defined along one edge or side by the dura mater which surrounds the spinal cord. The epidural space is further defined along a second edge or side by the periosteum of the bony vertebrae or by the ligamentum-flavum at the vertebral interspaces. Along the interior surface of the ligamentum-flavum lies the venus plexus, a complex configuration of veins. The epidural space contains fat, connective tissue, blood vessels, lymphatic vessels, nerve fibers, and other structures. Various lesions, cystical masses, and nerve damage can occur in and around the epidural space which causes various back problems for the human body.

Although applying anesthesia to the epidural space has been known for procedures such as child birth or the like, the anatomy of the epidural space and related structures has not been fully investigated. Conventionally, the insertion of a catheter, fluid introducer, or the like for inducing spinal anesthesia directly into the subarachnoid space of the spinal column, such as seen in U.S. Pat. No. 5,232,442 by Johnson, et al. entitled “Method And Apparatus For Inducing Anesthesia”, has been through fluoroscopic or radiographic observation. Fluoroscopic observation techniques have also been used to try to locate the various sources of problems associated with back pain such as seen in U.S. Pat. No. 5,215,105 by Kizelshteyn, et al. entitled “Method Of Treating Epidural Lesions”. The fluoroscopic techniques are helpful for general guidance of instruments or other devices, but fail to give the physician or other medical personnel a detailed picture of structures within vessels or cavities, such as the epidural space, and therefore are limited in identifying the source of back pain problems.

Also, endoscopes have been used whereby internal areas or organs within a body vessel or cavity may be observed by inserting an elongated insertable part of the endoscope through a tube or sleeve inserted into a body vessel or cavity, or directly into the body vessel or cavity itself, such as seen in U.S. Pat. No. 5,195,541 by Obenchain entitled “Method Of Performing Laparoscopic Lumbar Discectomy”. An endoscope, as used herein, is an instrument for examining the interior of a bodily canal or hollow organ. A catheter, on the other hand, is a tube inserted into a bodily channel, such as a vein, to maintain an opening to a body vessel or cavity. These endoscopes, however, are relatively large with respect to a catheter and, therefore, do not cooperate with a catheter for performing delicate surgery such as the type surrounding the back or spinal column.

Further, fiber optic scopes or fiberscopes have been used for various types of surgery such as surrounding the heart. These fiberscopes often are inserted into a vein or an artery for viewing blockage or the like within the vein or artery. The epidural space, however, has not fully been explored using visual techniques because the epidural space, as described above, does not take the form of a vein or artery. Because the epidural space collapses around an instrument or device inserted therein such as a catheter, an endoscope, a fiberscope, or a cutting tool, the space has not been considered for optical scope viewing or for performing many types of epidural surgical procedures.

Therefore, there is still a need for a method of epidural surgery that allows a physician to effectively enter the epidural space of a patient, visually observe and document a problem area which could be the source of back pain in the patient, and therapeutically treat the problem area in or around the epidural space in a minimal amount of time and with minimal amount of cutting and other potential damage to the patient during surgery.

SUMMARY OF THE INVENTION

The present invention provides a method of epidural surgery that improves visibility in the epidural space of a patient for more effectively conducting therapeutic surgery therein. The method of epidural surgery involves distending a portion of the epidural space by filling the portion of the epidural space with a fluid supplied from a catheter positioned in the epidural space and positioning a portion of an optical scope in the distended portion of the epidural space by inserting the optical scope through the catheter to thereby provide a visual image of the epidural space. The method of epidural surgery also allows a physician, or other medical personnel, to control and manipulate the catheter and an imaging source while simultaneously using surgical tools, such as fiberoptic scopes or the like, and fluids needed for medical operations to thereby allow the physician to positionally locate, isolate, and view problem areas within the epidural space. Because the method of epidural surgery minimizes cutting and other potential damage to the patient during surgery, the invention provides a method of epidural surgery that often can be performed as an outpatient procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects and advantages of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a fragmentary skeletal view of a human body illustrating spinal column regions thereof;

FIG. 2 is a fragmentary view of a spinal column illustrating the position of the epidural space therein;

FIG. 3 is an elevational plan view of a surgical operation on a patient having a catheter positioned through an opening in the sacrum region and into the epidural space by a physician for therapeutic treatment of a problem area according to a first embodiment of the present invention;

FIG. 4 is perspective view of an imaging apparatus for the methods according to the present invention;

FIG. 5 is a side elevational view of a catheter having a fiberscope inserted therein for the methods according to the present invention;

FIG. 6 is a perspective view of a catheter having a fiberscope inserted therein for the methods according to the present invention;

FIG. 7 is fragmentary top elevational view of a catheter for the methods according to the present invention;

FIG. 8 is an enlarged cross-sectional view of a first embodiment of a catheter taken along line 8—8 of FIG. 7 for the methods according to the present invention;

FIG. 9 is an enlarged cross-sectional view of a second embodiment of a catheter taken along line 8—8 of FIG. 7 for the methods according to the present invention;

FIG. 10 is an enlarged distal end plan view of a catheter taken from a distal end thereof for the methods according to the present invention;

FIG. 11 is enlarged fragmentary top plan view of a distal end of a catheter and having phantom lines therein illustrating the positioning of the multiple lumens within the catheter for the methods according to the present invention;

FIG. 12 is enlarged fragmentary side plan view of a distal end of a catheter for the methods according to the present invention;

FIG. 13 is a block diagram of a method of epidural surgery according to a first embodiment of the present invention; and

FIG. 14 is a block diagram of a method of epidural surgery according to a second embodiment of the present invention.

DESCRIPTION OF ILLUSTRATED EMBODIMENTS

The present invention now will be described more fully hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. Like numbers refer to like elements throughout.

In the back region or posterior end of the human body, as best illustrated in FIGS. 1 and 2, the epidural space 20 is potential space located in and extending the length of the spine 18. As illustrated in the fragmentary view of a spinal region 18 in FIG. 2, the epidural space 20 has a generally cylindrical or crescent type shape and is defined along one edge or side by the dura mater 22 which surrounds the spinal cord 19. The epidural space is further defined along a second edge or side by the periosteum of the bony vertebrae 23 or by the ligamentum-flavum 24 at the vertebral interspaces 25. Along the interior surface of the ligamentum-flavum 24 lies the venus plexus 26, a complex configuration of veins. The epidural space 20 is a collapsible potential space that contains fat, connective tissue, blood vessels, lymphatic vessels, nerve fibers, and other structures. Various lesions, cystical masses, and nerve damage can occur in and around the epidural space which causes various back problems for the human body. For example, fibrosis ranging from soft to tougher scar tissue may form randomly or in layers and adhere to the dura mater 22 and the periosteum of the body vertebrae 20 or the. ligamentum-flavum 24 which form lesions extending across the epidural space 20. These lesions can be caused by post operative scarring of nerves such as from laminectomy procedures. A ruptured, leaking, or torn disk can also cause lesions which are often the source of back pain.

The method of epidural surgery according to the present invention improves visibility in the epidural space 20, of a patient for more effectively conducting therapeutic surgery in and around the epidural space 20 such as applying a steroic fluid, performing a diskectomy, or disrupting a fibrotic lesion. The method of epidural surgery according to the present invention involves distending a portion of the epidural space 20 by filling the portion of the epidural space 20 with a fluid, preferably a liquid such as a normal saline solution, supplied from a catheter 30 positioned in the epidural space 20. As best shown in FIGS. 3-6, a portion of an optical scope 60 is positioned in the distended portion of the epidural space 20 by inserting the optical scope 60 through the catheter 30 to thereby provide a visual image 100 of the epidural space 20.

According to first and second embodiments of the present invention, the catheter 30 may be one of the numerous types of catheters known to those skilled in the art, but preferably is a multi-lumen, steerable catheter 30 as best illustrated with reference to FIGS. 5-12. The multi-lumen, steerable catheter 30 preferably has a multiple durometer tube portion 40 extending outwardly from a handle portion 35 such as disclosed and described in copending U.S. patent applications Ser. No. 07/908,403 filed on Jul. 6, 1992 and Ser. No. 07/970,490 filed on Nov. 2, 1992 which are hereby incorporated herein by reference. The optical scope 60 is preferably an 0.88 millimeter (mm) fiberscope, known to those skilled in the art, that may be inserted through a lumen 42 of the steerable catheter 30, and preferably through a fiberoptic sheath 6 as shown in FIG. 5 and have a portion 62 thereof extend into the epidural space 20. The fiberscope 60 preferably communicates with an imaging apparatus such as disclosed and described in copending U.S. patent application Ser. No. 07/963,431 filed on Oct. 12, 1992 which is also hereby incorporated herein by reference. As such, further details of the steerable catheter 30, the optical scope 60, and the imaging apparatus 80 will not be discussed except in relation to the operation thereof for the methods of epidural surgery according to the present invention.

By providing the combination of the steerable catheter 30, the fiberscope 60, and the imaging apparatus 80, as illustrated in the elevational plan view of FIG. 3, a physician 17, or other medical personnel, can control and manipulate the catheter 30 and the imaging source 82 of the imaging apparatus 80 while simultaneously using surgical tools, such as cutting instruments or the like, and fluids needed for medical operations to thereby allow the physician to positionally locate, isolate, and view problem areas on a television monitor 84, i.e., cathode ray tube display device, within the epidural space 20. The imaging apparatus 80 enables the physician to not only observe the visual image 100 of the distended portion of the epidural space 20, but also provides a means for recording and documenting the problem area such as the video cassette recording 86 mounted below the imaging source 82 and television monitor 84 on the portable stand 88. Since the steerable catheter 30 is preferably quite flexible and maneuverable within the epidural space 20, as best shown in FIGS. 6 and 7, the method also provides less radical interspinal surgical operations because problem areas can more effectively be observed and accessed with the optical scope 60 and steerable catheter 30 combination. Because the imaging apparatus 80 is mounted on a stand 88 having wheels 87, as best shown in FIGS. 5, the physician 17, and other medical personnel, can position the apparatus 80 close to the operation site. The control panel 83 and imaging source 82 of the imaging apparatus 80 provides image 100 adjustments, focus, and magnification to assist in viewing the epidural space 20 and the problem area when the portion of the epidural space 20 is distended by the liquid. It will be understood that the distended portion of the epidural space 20 to be viewed is preferably an amount of the epidural space 20 less than the entire boundaries thereof, the boundaries or peripheries being previously defined and described with reference to FIG. 3.

More particularly with reference to the block diagrams illustrated in FIGS. 13 and 14, and the elevational plan view of a surgical operation in FIG. 3, the method of epidural surgery according to the present invention includes inserting a needle through the skin of a patient 120, preferably through a sacrum region 125 (FIG. 13) or a lumbar region 135 (FIG. 14) of the patient 120, and into the epidural space 20 to thereby provide an opening from the skin into the epidural space 20 of the patient 120.

As illustrated in FIG. 1, the sacrum region 125 is at a lower end of the spinal column 18 below L-5 and adjacent the pelvic region 28. The sacrum 125 is a triangular shape bone formed generally by five fused vertebrae, i.e., sacral vertebrae, that are wedged dorsally between the two hip bones of the pelvic region 28 in this region of the human anatomy. It will also be understood by those skilled in the art that the invention is also applicable to various animals for veterinarian epidural procedures. The lumbar region 135 extends from L-1 to L-5 between the sacrum region 125 at a lower end and the thorax region (T-1 to T-12) at an upper end. The thorax region (T-1 to T-12) from an upper part 150 (T-12) lumbar region 135 to neck.

As illustrated in FIG. 13, according to a first embodiment of a method of epidural surgery 160 according to the present invention, the patient is scrubbed in the sacrum region 125, preferably in an area around the sacral canal and up to the level of T-8 (FIG. 1) with wide prep iodine, as shown by block 161. The patient 120 is draped, the physician 17 is scrubbed, and dressed in a sterile gown (FIG. 3). The entry site is prepared and a one percent (1%) Xylocaine solution is injected to create a skin wheel. The patient 120 is then sedated with Versed which is individually titrated to the patient's needs. The patient is also monitored with pulse oximetry, EKG, and a blood pressure monitor 42.

After the patient is scrubbed and prepared, a needle, preferably an 18-gauge Touhy needle, is used to access the sacral foramen, as shown by block 162. The ligamentum-flavum 24 (FIG. 2) is pierced and the needle tip is inserted in the sacral hiatus. Under fluoroscopic guidance, as shown by block 163, a guide wire, preferably a 0.035-inch straight tip floppy guide wire, is inserted and advanced through the needle and into the epidural space. The guide wire is preferably radiopaque and formed of stainless steel with a Teflon coating. The physician 17 then preferably fluoroscopically observes the position of the guide wire in the epidural space 20 and advances the guide wire to a spinal level where a suspected problem area within the epidural space 20 may have originated. As shown by block 164, the needle is extracted from the epidural space 20 and preferably discarded.

The catheter 30, and preferably a multi-lumen, steerable catheter, is then inserted over the guide wire and into the opening to the epidural space 20, as shown by block 165. The guide wire functions as a guidance device as the catheter 30 is advanced into the sacral hiatus; Because the catheter 30 is preferably a steerable catheter, the handle 35 and flexible distal end 45 ease the advancement and positioning of the catheter 30 within and around the epidural space 20. Fluid is supplied, and preferably continuously supplied, to a lumen 42 of the steerable catheter 30 to thereby distend a portion of the epidural space 20. The fluid is preferably a liquid such as a normal saline solution. A normal saline bag can be accessed with an I.V. set and coupled to a three-way stop-cock, or valve for fluid regulation. A 20 cubic centimeter (cc) syringe is then coupled-to a second port of the three-way stop-cock. An access port to a lumen 42 of the catheter 30 is also preferably coupled to a third port of the stop-cock. The,fluid may also enter through tube portion 38 at a proximal end 37 at the handle portion 35 of the catheter 30 (as best shown in FIG. 6). The 20 cc syringe is used first to extract all the air bubbles from the I.V. set and then fill the I.V. set with a normal-saline, liquid solution for distention of the epidural space. Twenty cc's of saline can be infused into the epidural space 20, as shown by block 166. The 20 cc's are sufficient to increase the pressure in a portion of the epidural space 20 and create a cavity in which the nerve root or other structures can be observed. The position of the steerable-catheter 30 within. the epidural space may also be fluoroscopically observed. The catheter 30, like the guide wire, is also preferably radiopaque. Under such circumstances, the physician can advance the steerable catheter 30 under the fluoroscopical observation to the suspected problem area.

As shown by block 167, an optical scope 60, preferably a fiber optic scope or fiberscope, is then inserted preferably within another lumen 41 of the multi-lumen, steerable catheter 30. The fiberscope 60 can enter an access port in the handle portion 35, as best shown in FIG. 6, or enter at a proximal end 37 of the handle portion 35 as shown in FIG. 3 or 4. It will also. be understood that the fiberscope 60 can be inserted prior to the advancement of the catheter 30 in the epidural space 20. A portion of the optical scope 60 is advanced within the lumen 41 of the steerable catheter 30 and into the distended portion of the epidural space 20. The optical scope 60 preferably is not radiopaque and preferably will not extend into the epidural space 20 more than about one centimeter (cm). With the fluid distending a portion of the epidural space 20, the optical scope 60 can also be positioned within the distal tip 45 of catheter 30 and still view the distended portion of the epidural space 20. The optical scope 60 illuminates the distended portion of the epidural space 20 to thereby visualize and display the epidural space 20 and a problem area therein with the imaging apparatus 80, as shown by block 168. The catheter 30 can be manipulated to place the distal end 45 into an optimal position to avoid any adhesions or naturally occurring fat globules that could hinder the flow of drugs such as a steroic fluid or that could hinder positioning of instruments or devices used in surgical procedures. As shown by block 169, the catheter 30 is manipulated until the problem area such as an inflammation is recognized by its redness, increased vascularity, or other systems. The problem area is then observed and documented. As shown by block 171, a treatment is then performed to the problem area within the epidural space such as the applying of a steroic fluid to a nerve area, disrupting a fibrotic lesion, performing a diskectomy, or other types of procedures. These therapeutic treatments preferably include positioning a distal end 45 of the steerable catheter 30 adjacent the problem area within the epidural space 20 and treating the problem area within the epidural space 20 through a lumen 41 or 42 of the steerable catheter 30.

After performing the treatment, the catheter 30 is then slowly extracted and a dressing is placed at the site of entry, as shown by blocks 172, 173. The patient is observed, preferably for about two hours, then discharged, as shown by block 174. The patient's chart is completed and a one week follow-up appointment may be made.

As illustrated in FIG. 14, according to a second embodiment 180 of a method of epidural surgery of the present invention, a lumbar region 135 of the patient 120 is scrubbed and prepped, preferably in and around the L3-L4 area (FIG. 1), as shown by block 181. In this second embodiment, in contrast to the first embodiment as illustrated in FIG. 2, the patient 120 is preferably in a sitting position to spread the L1-L5 vertebrae to make access easier. It will also be understood that other sites of entry along the spinal column 18, besides the sacrum or caudal region 125 and lumbar region 135 of the patient 120, may be performed according to the present invention.

As shown by block 182, an 18-gauge Touhy needle is inserted into the interspinal space,. such as between L3 and L4, using the loss of resistance technique well known to those skilled in the art. The epidural space 20 is confirmed and a guide wire, preferably a 0.035-inch straight floppy top guide wire, is inserted and advanced through the needle to the spinal level where the suspected problem area may be located in and around the epidural space 20, as shown by blocks 185, 186. The needle is then extracted (block 185) and preferably discarded.

As shown by block 187, the catheter 30 is inserted and advanced over the guide wire to the suspected problem area. The epidural space 20 is then infused with a fluid, as previously described with reference to the first embodiment, and distended (block 187). A portion of the optical scope 60 is inserted and advanced through a lumen 41 of the catheter 30 and 10 into the distended portion of the epidural space 20, as shown by block 188. The problem area is observed and documented, and the catheter is manipulated and positioned adjacent the problem area for more effectively performing a therapeutic procedure, such as previously described (blocks 189, 191). A therapeutic procedure is then performed, also as previously described, as shown by block 192. The catheter 30 is then slowly extracted, the entry site is dressed, and the patient is observed (blocks 193-195). A follow-up visit is then scheduled and the patient discharged.

The method of the present invention thereby provides improved visualization of the epidural space and more effective treatment of problems areas therein.

The method allows the physician to effectively observe and document the problem area and then determine the most effective treatment for the patient. Since the steerable catheter is preferably quite flexible and maneuverable within the epidural space, the method also provides less radical interspinal surgical operations because problem areas can more effectively be observed and accessed with the optical scope and steerable catheter combination.

In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purposes of limitation. The invention has been described in considerable detail with specific reference to various embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the invention as described in the foregoing specification and defined in the following appended claims. 

That which is claimed is:
 1. A method of enhancing viewing within the epidural space of a patient during an epidural procedure, the method comprising: inserting a distal end portion of a steerable catheter through an opening in a patient and into the epidural space, the steerable catheter having a plurality of lumen formed in an elongate tube portion having a tube diameter, said plurality of lumen including at least a first working lumen and a second working lumen, each of said first and second working lumen having distinct, non-coincident longitudinal axes, each of said first and second working lumen being separated from each other by a portion of the elongate tube, with each of said first and second working lumen being substantially symmetrically positioned along both sides of said tube diameter, a handle connected to the elongate tube portion, at least one access port connected to the handle and in fluid communication with the elongate tube portion to provide access to the plurality of lumen, and a steering controller connected to the handle and associated with the elongate tube to steeringly control movement of at least the distal end of the elongate tube portion; passing a fluid through said first working lumen of the steerable catheter; distending a portion of the epidural space of the patient by filling the portion of the epidural space with the fluid supplied from the steerable catheter to thereby create a fluid cavity within the epidural space; inserting a fiber optic scope through the second working lumen of the same steerable catheter when the distal end portion of the same steerable catheter is positioned in the epidural space; viewing the fluid cavity by use of the inserted fiber optic scope; and steering the steerable catheter to a structure within the epidural space for further viewing.
 2. A method as defined in claim 1, wherein the step of inserting a fiber optic scope includes the step of connecting the fiber optic scope to an imaging apparatus which displays the visual image received from the fiber optic scope.
 3. A method as defined in claim 1, wherein the step of distending a portion of the epidural space includes the step of supplying fluid to the steerable catheter and to the epidural space from the steerable catheter to the extent to maintain the portion of the epidural space in an open position for adequately visualizing the epidural space.
 4. A method as defined in claim 1, wherein the step of inserting a fiber optic scope includes the step of advancing the fiber optic scope through the second working lumen of the steerable catheter and into the epidural space.
 5. A method as defined in claim 1, wherein the step of passing a fluid through the first working lumen includes continuously supplying fluid through the first working lumen to the epidural space.
 6. A method as defined in claim 5, wherein the step of steering includes advancing the distal end portion of the tube portion to a suspected problem area, and wherein the method further comprises treating the suspected problem area through at least one of the plurality of lumen of the steerable catheter.
 7. A method as defined in claim 1, wherein said elongate tube portion is substantially circular in shape, said first working lumen having a first cross-sectional diameter, said second working lumen having a second cross-sectional diameter, the first and second cross-sectional diameters being substantially coincident with the tube diameter of said substantially circular elongate tube portion.
 8. A method as defined in claim 7, wherein the first and second cross-sectional diameters are substantially unequal in size.
 9. A method as defined in claim 1, wherein distending the portion of the epidural space comprises delivering the fluid supplied from the steerable catheter into the epidural space in a direction substantially parallel with a line of sight extending from the fiber optic scope to a portion of the fluid cavity viewed by the fiber optic scope, the line of sight being defined as an imaginary line from the fiber optic scope to the portion of the fluid cavity viewed by the fiber optic scope.
 10. A method as defined in claim 1, wherein distending the portion of the epidural space comprises directing the delivery of fluid supplied from the steerable catheter into the epidural space so as to create sufficient fluid pressure against the preselected portion of tissue to thereby create a fluid cavity.
 11. A method as defined in claim 1, wherein distending the portion of the epidural space comprises connecting a syringe containing the fluid to said first working lumen, injecting fluid from the syringe into said first working lumen, and conveying the fluid through said first working lumen into the portion of the epidural space.
 12. A method as defined in claim 1, wherein distending the portion of the epidural space comprises positioning a fluid container in fluid communication with said first working lumen, delivering fluid from the container into the first working lumen and conveying the fluid through the first working lumen into the portion of the epidural space.
 13. A method as defined in claim 12, wherein distending the portion of the epidural space further comprises regulating fluid pressure within the fluid cavity by interposing a stop-cock in fluid communication with and between the container and said first working lumen to thereby control the amount of fluid supplied to the fluid cavity and the rate at which the fluid is supplied.
 14. A method as defined in claim 1, wherein distending the portion of the epidural space comprises directing the delivery of fluid supplied from the steerable catheter into the epidural space to a preselected portion of tissue within the epidural space so as to create sufficient fluid pressure against the portion of tissue to thereby create and maintain a fluid cavity.
 15. A method as defined in claim 1, wherein continuously supplying a fluid through the first working lumen of said steerable catheter, and into the epidural space, comprises providing a stop-cock having at least three access ports defining first, second, and third access ports respectively, connecting the steerable catheter to the first access port, connecting a syringe containing fluid to the second access port, and connecting a fluid container to the third access port.
 16. A method as defined in claim 15, wherein continuously supplying a fluid through the steerable catheter and into the epidural space comprises opening the first and second access ports to permit injection of the fluid from the syringe into the steerable catheter and through the steerable catheter into the epidural space to thereby distend the portion of the epidural space, closing the second access port and opening the third access port to permit fluid to flow from the container into the steerable catheter and through the steerable catheter in to the epidural space to thereby maintain the portion of the epidural space in a distended state.
 17. A method as defined in claim 15, wherein the injection of the fluid from the syringe into the steerable catheter and through the steerable catheter into the epidural space comprises injecting fluid from a syringe capable of delivering at least twenty cubic centimeters (20 cc) of fluid into the steerable catheter and through the steerable catheter into the epidural space.
 18. A method as in claim 15, wherein the flow of fluid from the container into the steerable catheter and through the steerable catheter into the epidural space comprises permitting fluid to flow into the steerable catheter from a pliable intravenous (I.V.) bag.
 19. A method as defined in claim 18, wherein continuously supplying fluid through the steerable catheter and into the epidural space comprises controlling the amount of fluid supplied into the epidural space and the rate at which fluid is supplied into the epidural space from the I.V. bag using the third access port of the stop-cock. 